Supplementary Figure 3: Inactivation of the thalamus

Two approaches were used to inactivate the thalamus, primarily targeting the intralaminar nuclei. (a) Response of a striatal neuron to cerebellar stimulation before, during, and 1 hour post infusion of QX-314 into the thalamus. The infusion cannula was stereotaxically placed to target CL although it is likely that the adjoining intralaminar nuclei might have also been affected. Note partial recovery during the washout period. (b) To test whether specifically inactivating the thalamic neurons would attenuate striatal responses to cerebellar stimulation, the inhibitory light sensitive opsin ArchT was expressed by stereotaxically injecting an AAV targeting the centrolateral nucleus of the thalamus. As can be seen from Arch-GFP expression in green (DAPI staining in blue) Arch was expressed to large extent in the CL and the adjoining regions. The fiber optic was also stereotaxically implanted to target CL, further narrowing the area which was optogenetically manipulated. The fiber optic injury tract is indicated by red arrows and shows that CL was accurately targeted. Abbreviations: LHb, lateral habenula; LDDM, laterodorsal thalamic nucleus, dorsomedial part; HP, hippocampus; CL, centrolateral thalamus; MDL, mediodorsal thalamic nucleus, lateral part; PC, paracentral nucleus of the thalamus; CM, centromedial thalamus; (c) To examine the firing rates elicited by ArchT inactivation, we performed single-unit optrode recordings from thalamic neurons in awake, head-restrained animals (n=7, N=3). Activation of ArchT significantly decreased the firing rate of the thalamic neurons by approximately 80% (****=p<0.0001, one-tailed student’s t-test) for the duration of the 1 second pulse. Data shown in the left panel are normalized to the mean firing rate. S.E.M. is indicated in the dotted-red lines. Mean ± S.E.M. shown in the right panel.